Washington officials have pledged to increase security at the US state's psychiatric hospitals after a week in which two patients escaped and another two went missing.

A man accused of torturing a 20-year-old woman to death in 2013 was recaptured on Friday night after a two-day, cross-state manhunt which some feared would not end peacefully.

Spokane sheriff's spokesman Mark Gregory gave much of the credit for Anthony Garver's capture to a police dog named Gunnar, who found Garver hiding in the woods near his family home in Spokane.

The Washington Corrections Department has taken custody of Garver, who is now being held at Airway Heights Correction Centre in eastern Washington.

Garver, 28, escaped from Western State Hospital across the state in Lakewood on Wednesday night. He crawled out of the window of a locked, lower-security unit with another patient, Mark Alexander Adams, 58, who was caught the next day.

On Saturday, officials at the state health agency said security is being enhanced at Washington state psychiatric hospitals in the wake of the escape.

They are focused on boosting security in the Lakewood hospital's civil commitment area, where Garver and Adams recently were transferred from the criminal section, according to a statement from the department. The men were moved because of a change in the state's Involuntary Treatment Act, the agency said.

Garver was under a civil commitment after he finished serving his incarceration period, said Jeremy Barclay, corrections spokesman.

Two other patients took "unescorted leaves" from the hospital during the manhunt, state officials said. One was on an escorted outing on campus and has not been found.

Another had been approved for discharge and was awaiting community placement but did not return from a visit to a fast-food restaurant. Seattle police found him on Saturday.

Garver and Adams' escape from inside the hospital is rare, but unauthorised leaves are not, said Carla Reyes, assistant secretary for the health agency's Behavioural Health Administration.

"However, two unauthorised leaves and two escapes in one week is unacceptable, and immediate steps are being taken to improve security at the facility and to retrain staff," she said in a statement.

"The safety of the public, the patients and staff is paramount."

The hospital also has restricted patient movement on the grounds of Western State and outside the hospital for the weekend.

Also on Saturday, governor Jay Inslee expressed concern about the way the hospital is being operated and said he expects swift action to prevent future escapes.

"This incident put the public at risk, the staff at risk and the patients at risk," Mr Inslee said in a statement. "This raises serious questions once again about the management and operation of this troubled hospital."

The escapes also intensified federal scrutiny on Western State Hospital, Washington's largest psychiatric facility.

US regulators are already investigating a recent violent attack on a worker and a patient-on-patient sexual assault at the hospital. A workplace inspection released this week found a series of missteps that posed safety risks, including unlocked rooms and unattended items that could be used as weapons.

The Centres for Medicare and Medicaid Services has repeatedly cited the facility over safety concerns and threatened to cut millions in federal funding.

Garver was charged in 2013 with tying a 20-year-old woman to her bed with electrical cords, stabbing her 24 times in the chest and slashing her throat, prosecutors said.

After Garver escaped, he bought a bus ticket to Spokane, where his parents live. Garver had been last seen in the Spokane area, nearly 250 miles from Lakewood, after his father called authorities to report his son had stopped by briefly.